Fascicle II.3 _ Rec. E.521 11 All drawings appearing in this Recommendation have been done in Autocad. Recommendation E.521 CALCULATION OF THE NUMBER OF CIRCUITS IN A GROUP CARRYING OVERFLOW TRAFFIC A calculation of the number of circuits in a group carrying overflow traffic should be based on this Recommendation and on Recommendation E.522 dealing with high_usage groups. The objective grade of service used is that the average blocking during the busy_hour busy_hour of the 30 busiest days of the year will not exceed 1%. To determine the number of circuits in a group carrying overflow traffic group carrying overflow traffic, three traffic parameters are required: the average traffic offered to the group, the weighted peakedness factor weighted peakedness factor, and the level of day_to_day traffic variations. The level of day_to_day traffic variations indicates the degree to which the daily busy_hour traffic deviates from the overall mean traffic, and is determined by the sample variance of the 30 busy_hour traffic. The peakedness factor indicates the degree to which the variability of the traffic deviates from pure chance traffic within a single hour, and in statistical terms is the variance_to_mean ratio of the distribution of simultaneous overflow traffic. 1 Determination of the level of day_to_day traffic variations Let M1, M2, . . ., M30 denote the 30 busy_hour loads of the traffic offered to the final group. Determine the mean traffic M of the daily traffic by Equation was removed from the ASCII text version of this document. Determine the sample variance Vd of the daily traffic by Equation was removed from the ASCII text version of this document. Determine the point (M, Vd) on Figure 1/E.521; M on the horizontal axis, and Vd on the vertical axis. i)If the point (M, Vd) is below the bottom curve, the level of variation is Null. ii) If the point is between the lower two curves, the level of variation is Low. iii) If the point is between the upper two curves, the level of variation is Medium. iv) If the point is above the highest curve, the level of variation is High. Default procedures: if the data are not available to compute the variance Vd use the following guidelines: a)If no more than 25 per cent of the traffic offered to the final group is overflow from other groups, assume the level of day_to_day variation is Low. b)Otherwise, assume a Medium level of variation. Figure 1/E.521 - CCITT 48080 2 Determination of peakedness factor z Peakedness factors depend principally upon the number of high_usage circuits over which random traffic has access. When the number of such high_usage circuits does not exceed 30, the actual peakedness of the traffic overflowing from a high_usage group will be only slightly below the maximum peakedness values1),2). The maximum peakedness values are given in Table 1/E.521. TABLE 1/E.521 Maximum peakedness factor zi Number of Peakedness Number of Peakedness high_usage factor high_usage factor circuits (zi) circuits (zi) (ni) (ni) 1 1.17 16 2.44 2 1.31 17 2.49 3 1.43 18 2.55 4 1.54 19 2.61 5 1.64 20 2.66 6 1.73 21 2.71 7 1.82 22 2.76 8 1.90 23 2.81 9 1.98 24 2.86 10 2.05 25 2.91 11 2.12 26 2.96 12 2.19 27 3.00 13 2.26 28 3.05 14 2.32 29 3.09 15 2.38 30 3.14 For more than 30 circuits, the peakedness of the traffic overflowing from a high_usage group i of ni circuits is given by Equation was removed from the ASCII text version of this document. where Aiis the mean (random) traffic offered to the ni circuits and áiis the traffic overflowing. The overflow traffic ái is found by employing the standard Erlang loss formula E1, ni (Ai): Equation was removed from the ASCII text version of this document. The weighted mean peakedness factor z, is then calculated from: Equation was removed from the ASCII text version of this document. for the h parcels of traffic being offered to the final group. Note that for the traffic directly offered to the final group, the peakedness factor is zi = 1. 3 Determination of the mean traffic offered to the final group and the number of circuits required 3.1 For planning future network requirements, the traffic overflowing to a final group should be determined theoretically from forecasts of traffics offered to the high_usage groups. The mean traffic overflowing to the final group from a high_usage group high_usage group is determined in two steps: i)the "single_hour" overflow traffic ái overflowing from ni circuits is given as above by Equation was removed from the ASCII text version of this document. when Ai is the forecast of traffic offered to the ith high_usage group; ii) the average overflow traffic overflowing from the ni circuits is then determined by adjusting the single_hour traffic ái for the effect of day_to_day traffic variations. Equation was removed from the ASCII text version of this document. The adjustment factor ri is given in Table 2/E.521; it is a function of: _ the offered traffic Ai, _ the traffic AiEi, ni_1 (Ai) _ ái carried by the last trunk i, and _ the level of day_to_day variations of the traffic offered to the high_usage group. This level can be determined using the method described in 1 above, but applying it to measurements of traffic offered to the high_usage group. If such measurements are not available a medium level can be used. The mean traffic offered to the final group is then the sum of all over the h parcels of traffic: Equation was removed from the ASCII text version of this document. It can be assumed that the level of day_to_day traffic variations on the final group remains constant over the forecast time period. Using the level of day_to_day traffic variation as determined in 1 above on the final group and the peakedness factor of 2 above, the appropriate table of Tables 3/E.521 to 6/E.521 is used to derive the number of circuits required. Note 1 _ This method of calculation of the mean traffic offered to the final group is valid only if the overflow traffic due to blocking encountered in the exchange in the attempts to connect to a high_usage, is negligible. Note 2 _ Table 3/E.521 differs slightly from the previous tables published by CCITT, although in Table 3.1/E.521 there is no allowance for day_to_day variations. The new table takes into account a systematic bias in the measurement procedure that is based on a finite period of time (1 hour), instead of an infinite period as was assumed in the previous table [5]. Note 3 _ Tables 4/E.521, 5/E.521 and 6/E.521 are based on the calculation of the average blocking from the formula: Equation was removed from the ASCII text version of this document. where B(m) is the single_hour expected blocking and f(m) is the density distribution of day_to_day traffic (m), assuming a Pearson Type III distribution: Equation was removed from the ASCII text version of this document. M and Vd are the mean and day_to_day variance of the traffic as calculated [5] in 1 above. TABLE 2/E.521 Overflow adjustment for high_usage trunk groups Factor ri Last trunk traffic Offered traffic Low daily Medium daily High daily Ai variation variation variation 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 25 3 4 5 6 25 3 4 5 6 25 3 4 5 6 3 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 0 0 0 0 0 1 1 1 0 0 2 2 1 1 0 7 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 0 0 0 0 0 2 2 1 1 0 4 3 2 1 1 10 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1 1 1 0 0 3 2 2 1 1 5 4 3 2 1 15 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 2 1 1 1 0 5 4 2 2 1 8 6 4 3 1 20 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 2. 1. 1. 1. 1. 2 2 1 1 0 6 5 3 2 1 0 8 5 3 2 25 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 2. 2. 1. 1. 1. 3 2 2 1 1 8 6 4 3 1 3 0 7 4 2 30 1. 1. 1. 1. 1. 1. 1. 1. 1. 1. 2. 2. 1. 1. 1. 3 3 2 1 1 8 7 4 3 2 4 1 7 5 3 TABLE 3/E.521 Single_hour capacity, in Erlangs, as a function of the number of trunks and of the peakedness factor Parameters: _ Blockage 0.01; _ No allowance for day_to_day variation; _ Weighted mean peakedness factor. Numb er 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 4. of 0 2 4 6 8 0 2 4 6 8 0 4 8 0 trun ks requ ired 1 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 06 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 22 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 53 33 0 0 0 0 0 0 0 0 0 0 0 0 4 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 94 69 50 0 0 0 0 0 0 0 0 0 0 0 5 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 42 14 89 67 0 0 0 0 0 0 0 0 0 0 6 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 97 64 36 08 0 0 0 0 0 0 0 0 0 0 7 2. 2. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 56 19 86 58 31 0 0 0 0 0 0 0 0 0 8 3. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 19 81 44 11 81 53 0 0 0 0 0 0 0 0 9 3. 3. 3. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 83 42 03 67 36 03 75 50 0 0 0 0 0 0 10 4. 4. 3. 3. 2. 2. 2. 2. 1. 0. 0. 0. 0. 0. 53 08 67 28 92 58 28 00 75 0 0 0 0 0 11 5. 4. 4. 3. 3. 3. 2. 2. 2. 1. 0. 0. 0. 0. 22 75 31 89 53 17 83 53 25 97 0 0 0 0 12 5. 5. 4. 4. 4. 3. 3. 3. 2. 2. 2. 0. 0. 0. 94 44 97 56 14 78 42 08 78 47 22 0 0 0 13 6. 6. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0. 0. 67 14 64 19 81 39 03 67 33 03 72 0 0 0 14 7. 6. 6. 5. 5. 5. 4. 4. 3. 3. 3. 2. 0. 0. 42 86 36 89 44 03 67 28 94 61 28 69 0 0 15 8. 7. 7. 6. 6. 5. 5. 4. 4. 4. 3. 3. 0. 0. 17 58 06 58 11 69 31 92 56 19 86 22 0 0 16 8. 8. 7. 7. 6. 6. 5. 5. 5. 4. 4. 3. 3. 0. 94 33 78 28 81 36 94 56 17 81 44 81 19 0 17 9. 9. 8. 8. 7. 7. 6. 6. 5. 5. 5. 4. 3. 3. 72 08 50 00 50 06 61 19 81 42 06 39 75 44 18 10 9. 9. 8. 8. 7. 7. 6. 6. 6. 5. 4. 4. 4. .5 83 25 72 22 75 31 86 44 06 69 97 31 00 0 19 11 10 10 9. 8. 8. 7. 7. 7. 6. 6. 5. 4. 4. .3 .6 .0 44 92 44 97 53 11 72 33 58 89 58 1 1 0 20 12 11 10 10 9. 9. 8. 8. 7. 7. 6. 6. 5. 5. .0 .3 .7 .1 67 14 67 22 81 39 97 22 50 17 8 9 8 9 21 12 12 11 10 10 9. 9. 8. 8. 8. 7. 6. 6. 5. .8 .1 .5 .9 .3 86 39 92 47 06 64 86 11 78 9 9 3 4 9 22 13 13 12 11 11 10 10 9. 9. 8. 8. 7. 6. 6. .7 .0 .3 .6 .1 .6 .0 61 17 72 31 50 75 39 2 0 1 9 4 1 8 23 14 13 13 12 11 11 10 10 9. 9. 8. 8. 7. 7. .5 .7 .0 .4 .8 .3 .8 .3 86 42 97 17 39 00 3 8 8 7 9 6 1 3 24 15 14 13 13 12 12 11 11 10 10 9. 8. 8. 7. .3 .5 .8 .2 .6 .0 .5 .0 .5 .1 67 83 03 64 6 8 9 2 4 8 6 3 6 1 25 16 15 14 14 13 12 12 11 11 10 10 9. 8. 8. .1 .3 .6 .0 .3 .8 .2 .7 .2 .8 .3 50 69 31 9 9 7 0 9 3 8 8 8 1 6 26 17 16 15 14 14 13 13 12 12 11 11 10 9. 8. .0 .2 .4 .8 .1 .5 .0 .5 .0 .5 .0 .1 36 94 3 2 7 1 7 8 3 0 0 3 6 9 27 17 17 16 15 14 14 13 13 12 12 11 10 10 9. .8 .0 .2 .5 .9 .3 .7 .2 .7 .2 .7 .8 .0 61 6 3 8 8 4 3 8 2 2 2 5 6 3 28 18 17 17 16 15 15 14 13 13 12 12 11 10 10 .6 .8 .0 .3 .7 .1 .5 .9 .4 .9 .4 .5 .6 .2 9 6 8 6 2 1 3 7 4 4 7 6 9 8 29 19 18 17 17 16 15 15 14 14 13 13 12 11 10 .5 .6 .8 .1 .5 .8 .2 .7 .1 .6 .1 .2 .3 .9 6 9 9 7 0 6 8 2 9 7 9 8 9 4 30 20 19 18 17 17 16 16 15 14 14 13 12 12 11 .3 .5 .7 .9 .2 .6 .0 .4 .9 .4 .9 .9 .0 .6 9 3 2 7 8 4 6 7 2 2 2 7 8 4 31 21 20 19 18 18 17 16 16 15 15 14 13 12 12 .2 .3 .5 .7 .0 .4 .8 .2 .6 .1 .6 .6 .7 .3 5 6 3 8 8 2 1 2 7 4 4 9 8 3 32 22 21 20 19 18 18 17 17 16 15 15 14 13 13 .1 .1 .3 .5 .8 .2 .5 .0 .4 .8 .3 .3 .4 .0 1 9 6 8 9 2 8 0 2 9 6 9 7 3 33 22 22 21 20 19 19 18 17 17 16 16 15 14 13 .9 .0 .1 .3 .6 .0 .3 .7 .1 .6 .1 .1 .1 .7 7 6 9 9 7 0 6 5 9 4 1 1 7 2 34 23 22 22 21 20 19 19 18 17 17 16 15 14 14 .8 .8 .0 .2 .4 .8 .1 .5 .9 .3 .8 .8 .8 .4 3 9 0 2 7 1 4 3 4 9 6 6 9 2 35 24 23 22 22 21 20 19 19 18 18 17 16 15 15 .6 .7 .8 .0 .2 .5 .9 .3 .6 .1 .6 .5 .6 .1 9 5 3 3 8 8 2 1 9 4 1 8 1 4 36 25 24 23 22 22 21 20 20 19 18 18 17 16 15 .5 .5 .6 .8 .1 .3 .7 .0 .4 .8 .3 .3 .3 .8 8 8 9 6 1 9 2 8 7 9 6 1 1 3 37 26 25 24 23 22 22 21 20 20 19 19 18 17 16 .4 .4 .5 .6 .9 .1 .5 .8 .2 .6 .1 .0 .0 .5 4 4 3 9 2 9 0 6 5 7 1 6 6 6 38 27 26 25 24 23 23 22 21 21 20 19 18 17 17 .3 .3 .3 .5 .7 .0 .3 .6 .0 .4 .8 .8 .7 .2 1 1 6 3 2 0 1 4 3 4 6 1 8 8 39 28 27 26 25 24 23 23 22 21 21 20 19 18 18 .1 .1 .2 .3 .5 .8 .1 .4 .8 .1 .6 .5 .5 .0 9 7 2 6 6 1 1 4 1 9 4 3 0 0 40 29 28 27 26 25 24 23 23 22 21 21 20 19 18 .0 .0 .0 .1 .3 .6 .8 .2 .5 .9 .3 .2 .2 .7 8 3 6 9 9 1 9 2 8 7 9 8 5 2 41 29 28 27 27 26 25 24 24 23 22 22 21 19 19 .9 .8 .9 .0 .1 .4 .6 .0 .3 .7 .1 .0 .9 .4 4 9 2 3 9 4 9 3 6 5 7 6 7 7 42 30 29 28 27 27 26 25 24 24 23 22 21 20 20 .8 .7 .7 .8 .0 .2 .5 .8 .1 .5 .9 .8 .7 .1 3 5 8 6 3 5 3 1 7 3 4 1 2 9 43 31 30 29 28 27 27 26 25 24 24 23 22 21 20 .7 .6 .6 .7 .8 .0 .3 .6 .9 .3 .6 .5 .4 .9 2 4 1 2 6 8 3 1 4 1 9 6 7 4 44 32 31 30 29 28 27 27 26 25 25 24 23 22 21 .6 .5 .4 .5 .6 .8 .1 .4 .7 .1 .5 .3 .2 .6 1 0 7 6 9 9 4 2 5 1 0 3 2 9 45 33 32 31 30 29 28 27 27 26 25 25 24 22 22 .5 .3 .3 .4 .5 .7 .9 .2 .5 .8 .2 .0 .9 .4 0 9 3 2 3 2 4 2 6 9 8 8 7 2 46 34 33 32 31 30 29 28 28 27 26 26 24 23 23 .3 .2 .1 .2 .3 .5 .7 .0 .3 .6 .0 .8 .7 .1 9 5 9 5 9 6 8 3 3 9 6 6 2 7 47 35 34 33 32 31 30 29 28 28 27 26 25 24 23 .2 .1 .0 .1 .2 .3 .5 .8 .1 .4 .8 .6 .4 .9 8 4 8 1 2 9 8 6 4 7 3 4 7 2 48 36 35 33 32 32 31 30 29 28 28 27 26 25 24 .1 .0 .9 .9 .0 .2 .4 .6 .9 .2 .6 .4 .2 .6 7 0 4 7 6 2 2 7 4 8 4 2 5 9 49 37 35 34 33 32 32 31 30 29 29 28 27 26 25 .0 .8 .8 .8 .9 .0 .2 .4 .7 .0 .4 .1 .0 .4 6 9 1 1 2 6 5 7 5 8 2 9 0 4 50 37 36 35 34 33 32 32 31 30 29 29 27 26 26 .9 .7 .6 .6 .7 .8 .0 .3 .5 .8 .2 .9 .7 .1 7 8 7 7 5 9 8 1 8 9 2 7 8 9 TABLE 4/E.521 Single_hour capacity, in Erlangs, as a function of the number of trunks and of the peakedness factor Parameters: _ Blockage 0.01; _ Low day_to_day variation allowance; _ Weighted mean peakedness factor. Numb er 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 4. of 0 2 4 6 8 0 2 4 6 8 0 4 8 0 trun ks requ ired 1 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 06 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 22 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 53 33 0 0 0 0 0 0 0 0 0 0 0 0 4 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 94 69 50 0 0 0 0 0 0 0 0 0 0 0 5 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 39 14 89 67 0 0 0 0 0 0 0 0 0 0 6 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 89 64 36 08 0 0 0 0 0 0 0 0 0 0 7 2. 2. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 44 14 86 58 31 0 0 0 0 0 0 0 0 0 8 3. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 03 69 42 11 81 53 0 0 0 0 0 0 0 0 9 3. 3. 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 64 28 97 67 36 03 75 50 0 0 0 0 0 0 10 4. 3. 3. 3. 2. 2. 2. 2. 1. 0. 0. 0. 0. 0. 25 89 56 22 92 58 28 00 75 0 0 0 0 0 11 4. 4. 4. 3. 3. 3. 2. 2. 2. 1. 0. 0. 0. 0. 92 53 17 83 50 17 83 53 25 97 0 0 0 0 12 5. 5. 4. 4. 4. 3. 3. 3. 2. 2. 2. 0. 0. 0. 58 17 78 44 08 78 42 08 78 47 22 0 0 0 13 6. 5. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0. 0. 25 81 42 06 69 36 03 67 33 03 72 0 0 0 14 6. 6. 6. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0. 94 50 08 69 33 97 64 28 94 61 28 69 0 0 15 7. 7. 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 0. 0. 64 17 75 33 97 61 25 92 56 19 86 22 0 0 16 8. 7. 7. 7. 6. 6. 5. 5. 5. 4. 4. 3. 3. 0. 33 86 42 00 61 25 89 53 17 81 44 81 19 0 17 9. 8. 8. 7. 7. 6. 6. 6. 5. 5. 5. 4. 3. 3. 06 56 11 67 28 89 53 17 81 42 06 39 75 44 18 9. 9. 8. 8. 7. 7. 7. 6. 6. 6. 5. 4. 4. 4. 81 28 81 36 94 56 17 81 44 06 69 97 31 00 19 10 10 9. 9. 8. 8. 7. 7. 7. 6. 6. 5. 4. 4. .5 .0 50 06 61 22 83 44 08 72 33 58 89 58 3 0 20 11 10 10 9. 9. 8. 8. 8. 7. 7. 6. 6. 5. 5. .2 .7 .2 75 31 89 50 11 72 36 97 22 50 17 8 2 2 21 12 11 10 10 10 9. 9. 8. 8. 8. 7. 6. 6. 5. .0 .4 .9 .4 .0 56 17 78 39 03 64 86 11 78 3 4 4 4 0 22 12 12 11 11 10 10 9. 9. 9. 8. 8. 7. 6. 6. .7 .1 .6 .1 .6 .2 83 44 06 67 31 56 75 39 8 9 7 7 9 5 23 13 12 12 11 11 10 10 10 9. 9. 8. 8. 7. 7. .5 .9 .3 .8 .4 .9 .5 .1 72 33 94 19 39 00 3 4 9 9 2 4 3 1 24 14 13 13 12 12 11 11 10 10 10 9. 8. 8. 7. .3 .6 .1 .6 .1 .6 .2 .8 .3 .0 61 86 03 64 1 9 4 1 1 7 2 1 9 0 25 15 14 13 13 12 12 11 11 11 10 10 9. 8. 8. .0 .4 .8 .3 .8 .3 .9 .5 .0 .6 .2 50 67 31 8 4 6 3 3 6 2 0 8 7 8 26 15 15 14 14 13 13 12 12 11 11 10 10 9. 8. .8 .2 .6 .0 .5 .0 .6 .1 .7 .3 .9 .1 33 94 6 2 1 8 6 8 1 9 5 6 4 7 27 16 15 15 14 14 13 13 12 12 12 11 10 10 9. .6 .9 .3 .8 .2 .8 .3 .8 .4 .0 .6 .8 .0 61 4 7 6 1 8 1 3 9 4 3 4 3 0 28 17 16 16 15 15 14 14 13 13 12 12 11 10 10 .4 .7 .1 .5 .0 .5 .0 .5 .1 .7 .3 .5 .6 .2 2 5 4 6 3 3 6 8 4 2 1 0 7 8 29 18 17 16 16 15 15 14 14 13 13 13 12 11 10 .2 .5 .8 .3 .7 .2 .7 .3 .8 .4 .0 .1 .3 .9 2 3 9 1 8 5 8 1 6 2 0 9 6 4 30 19 18 17 17 16 16 15 15 14 14 13 12 12 11 .0 .3 .6 .0 .5 .0 .5 .0 .5 .1 .6 .8 .0 .6 0 1 7 6 0 0 0 3 6 1 9 6 6 4 31 19 19 18 17 17 16 16 15 15 14 14 13 12 12 .8 .0 .4 .8 .2 .7 .2 .7 .2 .8 .3 .5 .7 .3 1 8 4 3 5 2 2 2 8 3 9 6 5 3 32 20 19 19 18 18 17 16 16 16 15 15 14 13 13 .6 .8 .1 .5 .0 .4 .9 .4 .0 .5 .1 .2 .4 .0 1 9 9 8 0 7 4 7 0 3 1 5 4 3 33 21 20 19 19 18 18 17 17 16 16 15 14 14 13 .3 .6 .9 .3 .7 .2 .6 .1 .7 .2 .8 .9 .1 .7 9 7 7 6 8 2 9 9 2 5 1 4 4 2 34 22 21 20 20 19 18 18 17 17 16 16 15 14 14 .2 .4 .7 .1 .5 .9 .4 .9 .4 .9 .5 .6 .8 .4 2 7 5 1 3 7 2 2 4 7 3 7 3 2 35 23 22 21 20 20 19 19 18 18 17 17 16 15 15 .0 .2 .5 .8 .2 .7 .1 .6 .1 .6 .2 .3 .5 .1 3 5 6 9 8 2 7 7 7 9 2 6 6 1 36 23 23 22 21 21 20 19 19 18 18 17 17 16 15 .8 .0 .3 .6 .0 .4 .9 .3 .8 .4 .9 .0 .2 .8 3 6 3 7 6 7 2 9 9 2 4 8 5 1 37 24 23 23 22 21 21 20 20 19 19 18 17 16 16 .6 .8 .1 .4 .8 .2 .6 .1 .6 .1 .6 .7 .9 .5 4 6 4 4 3 5 7 4 4 4 7 8 4 0 38 25 24 23 23 22 22 21 20 20 19 19 18 17 17 .4 .6 .9 .2 .6 .0 .4 .8 .3 .8 .4 .5 .6 .1 7 7 2 5 1 0 4 9 6 9 2 0 4 9 39 26 25 24 24 23 22 22 21 21 20 20 19 18 17 .2 .4 .7 .0 .3 .7 .1 .6 .1 .6 .1 .2 .3 .8 8 7 2 3 9 8 9 4 1 1 4 2 3 9 40 27 26 25 24 24 23 22 22 21 21 20 19 19 18 .1 .2 .5 .8 .1 .5 .9 .3 .8 .3 .8 .9 .0 .6 1 8 3 1 7 3 4 9 6 6 6 4 6 1 41 27 27 26 25 24 24 23 23 22 22 21 20 19 19 .9 .0 .3 .6 .9 .3 .7 .1 .6 .1 .6 .6 .7 .3 2 8 1 1 4 1 2 4 1 1 1 7 8 1 42 28 27 27 26 25 25 24 23 23 22 22 21 20 20 .7 .9 .1 .3 .7 .0 .4 .9 .3 .8 .3 .3 .4 .0 5 2 1 9 2 8 7 2 6 3 3 9 7 3 43 29 28 27 27 26 25 25 24 24 23 23 22 21 20 .5 .7 .9 .1 .5 .8 .2 .6 .1 .5 .0 .1 .1 .7 8 2 2 9 0 6 5 7 1 8 8 1 9 5 44 30 29 28 28 27 26 26 25 24 24 23 22 21 21 .4 .5 .7 .0 .3 .6 .0 .4 .8 .3 .8 .8 .9 .4 2 6 5 0 1 4 3 4 9 3 3 6 2 4 45 31 30 29 28 28 27 26 26 25 25 24 23 22 22 .2 .3 .5 .8 .0 .4 .8 .2 .6 .1 .5 .5 .6 .1 5 6 6 1 8 4 1 2 4 1 8 8 4 7 46 32 31 30 29 28 28 27 26 26 25 25 24 23 22 .0 .1 .3 .6 .8 .2 .5 .9 .4 .8 .3 .3 .3 .8 8 9 6 1 9 2 8 7 2 6 3 3 6 9 47 32 32 31 30 29 29 28 27 27 26 26 25 24 23 .9 .0 .1 .4 .6 .0 .3 .7 .1 .6 .0 .0 .1 .6 2 3 7 2 9 0 6 5 7 1 8 6 1 4 48 33 32 32 31 30 29 29 28 27 27 26 25 24 24 .7 .8 .0 .2 .4 .8 .1 .5 .9 .3 .8 .8 .8 .3 5 3 0 2 7 1 4 3 4 9 3 1 3 6 49 34 33 32 32 31 30 29 29 28 28 27 26 25 25 .5 .6 .8 .0 .2 .5 .9 .3 .7 .1 .5 .5 .5 .0 8 7 1 3 8 8 4 1 2 4 8 6 6 8 50 35 34 33 32 32 31 30 30 29 28 28 27 26 25 .4 .5 .6 .8 .0 .3 .7 .0 .5 .9 .3 .3 .3 .8 4 0 4 3 8 9 2 8 0 2 6 1 1 3 TABLE 5/E.521 Single_hour capacity, in Erlangs, as a function of the number of trunks and of the peakedness factor Parameters: _ Blockage 0.01; _ Medium day_to_day variation allowance; _ Weighted mean peakedness factor. Numb er 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 4. of 0 2 4 6 8 0 2 4 6 8 0 4 8 0 trun ks requ ired 1 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 06 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 22 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 53 33 0 0 0 0 0 0 0 0 0 0 0 0 4 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 94 69 50 0 0 0 0 0 0 0 0 0 0 0 5 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 39 14 89 67 0 0 0 0 0 0 0 0 0 0 6 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 86 61 36 08 0 0 0 0 0 0 0 0 0 0 7 2. 2. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 39 11 83 58 31 0 0 0 0 0 0 0 0 0 8 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 94 64 36 08 81 53 0 0 0 0 0 0 0 0 9 3. 3. 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 53 19 89 61 33 03 75 50 0 0 0 0 0 0 10 4. 3. 3. 3. 2. 2. 2. 2. 1. 0. 0. 0. 0. 0. 11 78 47 17 86 58 28 00 75 0 0 0 0 0 11 4. 4. 4. 3. 3. 3. 2. 2. 2. 1. 0. 0. 0. 0. 72 39 03 72 42 14 83 53 25 97 0 0 0 0 12 5. 4. 4. 4. 4. 3. 3. 3. 2. 2. 2. 0. 0. 0. 36 97 64 31 00 69 39 08 78 47 22 0 0 0 13 6. 5. 5. 4. 4. 4. 3. 3. 3. 3. 2. 0. 0. 0. 00 61 25 89 56 25 94 67 33 03 72 0 0 0 14 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0. 64 22 86 50 17 83 53 22 92 61 28 69 0 0 15 7. 6. 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 0. 0. 31 89 47 11 78 42 11 78 47 19 86 22 0 0 16 7. 7. 7. 6. 6. 6. 5. 5. 5. 4. 4. 3. 3. 0. 97 53 11 75 39 03 69 39 06 75 44 81 19 0 17 8. 8. 7. 7. 7. 6. 6. 5. 5. 5. 5. 4. 3. 3. 64 19 78 36 00 64 31 97 64 33 03 39 75 44 18 9. 8. 8. 8. 7. 7. 6. 6. 6. 5. 5. 4. 4. 4. 33 86 42 03 64 28 92 58 25 92 61 97 31 00 19 10 9. 9. 8. 8. 7. 7. 7. 6. 6. 6. 5. 4. 4. .0 53 08 67 28 89 53 19 86 53 19 58 89 58 3 20 10 10 9. 9. 8. 8. 8. 7. 7. 7. 6. 6. 5. 5. .6 .1 75 33 92 53 17 81 47 14 81 17 50 17 9 9 21 11 10 10 9. 9. 9. 8. 8. 8. 7. 7. 6. 6. 5. .4 .8 .4 97 56 17 81 44 08 75 42 75 11 78 2 9 2 22 12 11 11 10 10 9. 9. 9. 8. 8. 8. 7. 6. 6. .1 .5 .1 .6 .2 83 44 06 69 36 03 36 72 39 1 8 1 4 2 23 12 12 11 11 10 10 10 9. 9. 8. 8. 7. 7. 7. .8 .2 .7 .3 .8 .4 .0 69 33 97 64 97 33 00 3 8 8 3 9 7 8 24 13 13 12 12 11 11 10 10 9. 9. 9. 8. 7. 7. .5 .0 .4 .0 .5 .1 .7 .3 97 61 25 58 94 61 3 0 7 0 6 4 2 6 25 14 13 13 12 12 11 11 11 10 10 9. 9. 8. 9. .2 .6 .1 .6 .2 .8 .3 .0 .6 .2 89 19 56 19 5 9 7 9 5 1 9 0 1 5 26 14 14 13 13 12 12 12 11 11 10 10 9. 9. 8. .9 .4 .8 .3 .9 .4 .0 .6 .2 .8 .5 83 17 81 7 2 6 9 2 7 6 4 8 9 3 27 15 15 14 14 13 13 12 12 11 11 11 10 9. 9. .6 .1 .5 .0 .6 .1 .7 .3 .9 .5 .1 .4 78 42 9 1 8 8 1 4 2 1 2 3 7 4 28 16 15 15 14 14 13 13 12 12 12 11 11 10 10 .4 .8 .2 .7 .2 .8 .3 .9 .5 .1 .8 .0 .3 .0 4 3 8 8 8 3 9 7 8 9 1 8 9 6 29 17 16 16 15 14 14 14 13 13 12 12 11 11 10 .1 .5 .0 .4 .9 .5 .0 .6 .2 .8 .4 .7 .0 .6 7 6 0 7 7 3 8 4 5 3 7 2 3 7 30 17 17 16 16 15 15 14 14 13 13 13 12 11 11 .9 .2 .7 .1 .6 .1 .7 .3 .9 .5 .1 .3 .6 .3 2 8 2 7 7 9 5 1 2 0 1 6 4 1 31 18 18 17 16 16 15 15 15 14 14 13 13 12 11 .6 .0 .4 .8 .3 .8 .4 .0 .5 .1 .7 .0 .2 .9 4 3 2 9 9 9 4 0 8 7 8 3 8 4 32 19 18 18 17 17 16 16 15 15 14 14 13 12 12 .3 .7 .1 .5 .0 .5 .1 .6 .2 .8 .4 .6 .9 .5 9 5 4 8 8 8 1 7 5 3 4 7 2 6 33 20 19 18 18 17 17 16 16 15 15 15 14 13 13 .1 .4 .8 .3 .7 .2 .8 .3 .9 .5 .1 .3 .5 .1 4 7 6 1 8 8 1 6 2 0 1 3 8 9 34 20 20 19 19 18 18 17 17 16 16 15 14 14 13 .8 .2 .6 .0 .5 .0 .5 .0 .6 .1 .7 .9 .2 .8 9 2 1 3 0 0 0 6 1 7 8 7 2 6 35 21 20 20 19 19 18 18 17 17 16 16 15 14 14 .6 .9 .3 .7 .2 .6 .1 .7 .2 .8 .4 .6 .8 .5 4 7 3 5 2 9 9 5 8 6 4 4 6 0 36 22 21 21 20 19 19 18 18 17 17 17 16 15 15 .3 .6 .0 .4 .9 .4 .9 .4 .9 .5 .1 .3 .5 .1 9 9 6 7 2 2 2 4 7 3 1 1 3 4 37 23 22 21 21 20 20 19 19 18 18 17 16 16 15 .1 .4 .8 .1 .6 .1 .6 .1 .6 .2 .8 .9 .1 .8 4 4 1 9 4 1 1 4 7 2 1 7 9 1 38 23 23 22 21 21 20 20 19 19 18 18 17 16 16 .8 .1 .5 .9 .3 .8 .3 .8 .3 .9 .4 .6 .8 .4 9 9 3 4 6 3 1 3 6 2 7 4 6 7 39 24 23 23 22 22 21 21 20 20 19 19 18 17 17 .6 .9 .2 .6 .0 .5 .0 .5 .0 .6 .1 .3 .5 .1 4 4 8 7 8 6 3 3 6 1 7 3 3 1 40 25 24 24 23 22 22 21 21 20 20 19 19 18 17 .4 .6 .0 .3 .8 .2 .7 .2 .7 .3 .8 .0 .1 .7 2 9 3 9 1 5 5 5 5 1 6 0 9 8 41 26 25 24 24 23 22 22 21 21 21 20 19 18 18 .1 .4 .7 .1 .5 .9 .4 .9 .4 .0 .5 .6 .8 .4 7 4 8 4 6 7 4 4 7 0 6 9 6 4 42 26 26 25 24 24 23 23 22 22 21 21 20 19 19 .9 .1 .5 .8 .2 .7 .1 .6 .1 .6 .2 .3 .5 .1 4 9 0 6 8 2 7 7 7 9 5 6 3 1 43 27 26 26 25 25 24 23 23 22 22 21 21 20 19 .7 .9 .2 .6 .0 .4 .8 .3 .8 .3 .9 .0 .1 .8 2 7 5 1 0 4 9 6 6 9 4 6 9 1 44 28 27 27 26 25 25 24 24 23 23 22 21 20 20 .4 .7 .0 .3 .7 .1 .6 .0 .5 .0 .6 .7 .8 .4 7 2 0 6 5 7 1 8 8 8 4 5 9 7 45 29 28 27 27 26 25 25 24 24 23 23 22 21 21 .2 .4 .7 .1 .4 .8 .3 .8 .3 .8 .3 .4 .5 .1 5 7 8 1 7 9 3 1 1 1 3 4 6 4 46 30 29 28 27 27 26 26 25 25 24 24 23 22 21 .0 .2 .5 .8 .2 .6 .0 .5 .0 .5 .0 .1 .2 .8 3 5 3 6 2 4 6 3 0 0 3 4 5 3 47 30 30 29 28 27 27 26 26 25 25 24 23 22 22 .8 .0 .2 .6 .9 .3 .7 .2 .7 .2 .7 .8 .9 .5 1 0 8 1 7 6 8 5 2 2 5 3 4 0 48 31 30 30 29 28 28 27 26 26 25 25 24 23 23 .5 .7 .0 .3 .7 .1 .5 .9 .4 .9 .4 .5 .6 .1 8 8 3 6 2 1 3 7 4 4 4 3 4 9 49 32 31 30 30 29 28 28 27 27 26 26 25 24 23 .3 .5 .8 .1 .4 .8 .2 .6 .1 .6 .1 .2 .3 .8 6 6 1 1 4 3 5 9 7 4 7 2 3 9 50 33 32 31 30 30 29 29 28 27 27 26 25 25 24 .1 .3 .5 .8 .1 .5 .0 .4 .8 .3 .8 .9 .0 .5 4 1 6 6 9 8 0 2 9 6 6 2 3 8 TABLE 6/E.521 Single_hour capacity, in Erlangs, as a function of the number of trunks and of the peakedness factor Parameters: _ Blockage 0.01; _ High day_to_day variation allowance; _ Weighted mean peakedness factor. Numb er 1. 1. 1. 1. 1. 2. 2. 2. 2. 2. 3. 3. 3. 4. of 0 2 4 6 8 0 2 4 6 8 0 4 8 0 trun ks requ ired 1 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 06 0 0 0 0 0 0 0 0 0 0 0 0 0 2 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 22 0 0 0 0 0 0 0 0 0 0 0 0 0 3 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 53 33 0 0 0 0 0 0 0 0 0 0 0 0 4 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 94 69 50 0 0 0 0 0 0 0 0 0 0 0 5 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 36 14 89 67 0 0 0 0 0 0 0 0 0 0 6 1. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 0. 86 61 36 08 0 0 0 0 0 0 0 0 0 0 7 2. 2. 1. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 0. 36 08 83 58 31 0 0 0 0 0 0 0 0 0 8 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 0. 0. 89 61 33 06 81 53 0 0 0 0 0 0 0 0 9 3. 3. 2. 2. 2. 2. 1. 1. 0. 0. 0. 0. 0. 0. 44 14 86 58 31 03 75 50 0 0 0 0 0 0 10 4. 3. 3. 3. 2. 2. 2. 2. 1. 0. 0. 0. 0. 0. 03 69 39 11 83 56 28 00 75 0 0 0 0 0 11 4. 4. 3. 3. 3. 3. 2. 2. 2. 1. 0. 0. 0. 0. 61 25 94 64 36 08 81 53 25 97 0 0 0 0 12 5. 4. 4. 4. 3. 3. 3. 3. 2. 2. 2. 0. 0. 0. 19 83 50 19 89 61 33 06 78 47 22 0 0 0 13 5. 5. 5. 4. 4. 4. 3. 3. 3. 3. 2. 0. 0. 0. 81 42 08 78 44 17 86 58 31 03 72 0 0 0 14 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 3. 2. 0. 0. 42 03 67 33 03 72 42 14 83 58 28 69 0 0 15 7. 6. 6. 5. 5. 5. 4. 4. 4. 4. 3. 3. 0. 0. 03 64 28 92 61 28 97 69 39 11 83 22 0 0 16 7. 7. 6. 6. 6. 5. 5. 5. 4. 4. 4. 3. 3. 0. 67 25 86 53 19 86 56 25 94 67 36 81 19 0 17 8. 7. 7. 7. 6. 6. 6. 5. 5. 5. 4. 4. 3. 3. 31 86 47 11 78 44 11 81 50 22 92 36 75 44 18 8. 8. 8. 7. 7. 7. 6. 6. 6. 5. 5. 4. 4. 4. 94 50 11 72 36 03 69 39 08 78 47 89 31 00 19 9. 9. 8. 8. 7. 7. 7. 6. 6. 6. 6. 5. 4. 4. 58 14 72 33 97 64 31 97 64 33 03 44 89 58 20 10 9. 9. 8. 8. 8. 7. 7. 7. 6. 6. 6. 5. 5. .2 78 36 94 58 22 89 56 22 92 61 00 44 14 2 21 10 10 9. 9. 9. 8. 8. 8. 7. 7. 7. 6. 6. 5. .8 .4 97 58 19 83 50 14 83 50 19 58 00 69 9 2 22 11 11 10 10 9. 9. 9. 8. 8. 8. 7. 7. 6. 6. .5 .0 .6 .2 83 44 08 75 42 08 78 17 56 25 3 6 1 2 23 12 11 11 10 10 10 9. 9. 9. 8. 8. 7. 7. 6. .1 .7 .2 .8 .4 .0 69 36 00 67 36 72 14 83 9 2 8 3 4 6 24 12 12 11 11 11 10 10 9. 9. 9. 8. 8. 7. 7. .8 .3 .9 .4 .0 .6 .3 94 61 28 94 31 69 39 6 6 2 7 8 9 1 25 13 13 12 12 11 11 10 10 10 9. 9. 8. 8. 7. .5 .0 .5 .1 .6 .3 .9 .5 .2 89 56 92 28 97 3 3 6 1 9 1 4 6 2 26 14 13 13 12 12 11 11 11 10 10 10 9. 8. 8. .1 .6 .2 .7 .3 .9 .5 .1 .8 .4 .1 50 86 56 9 9 2 5 3 4 6 9 3 7 4 27 14 14 13 13 12 12 12 11 11 11 10 10 9. 9. .8 .3 .8 .4 .9 .5 .1 .8 .4 .0 .7 .0 44 14 9 6 6 2 7 8 9 1 4 8 5 8 28 15 15 14 14 13 13 12 12 12 11 11 10 10 9. .5 .0 .5 .0 .6 .2 .8 .4 .0 .6 .3 .6 .0 72 6 3 3 6 4 2 1 2 6 9 6 9 3 29 16 15 15 14 14 13 13 13 12 12 11 11 10 10 .2 .6 .1 .7 .2 .8 .4 .0 .6 .3 .9 .3 .6 .3 5 9 9 2 8 6 4 6 9 3 7 1 4 1 30 16 16 15 15 14 14 14 13 13 12 12 11 11 10 .9 .3 .8 .3 .9 .5 .0 .6 .3 .9 .5 .8 .2 .9 2 6 6 6 2 0 8 9 1 4 8 9 2 2 31 17 17 16 16 15 15 14 14 13 13 13 12 11 11 .6 .0 .5 .0 .5 .1 .7 .3 .9 .5 .1 .5 .8 .5 1 6 3 3 8 4 2 3 4 6 9 0 3 0 32 18 17 17 16 16 15 15 14 14 14 13 13 12 12 .3 .7 .1 .6 .2 .7 .3 .9 .5 .1 .8 .1 .4 .1 1 2 9 9 2 8 6 4 6 9 3 1 4 1 33 18 18 17 17 16 16 16 15 15 14 14 13 13 12 .9 .4 .8 .3 .8 .4 .0 .5 .1 .8 .4 .7 .0 .6 7 2 6 6 9 4 0 8 9 1 4 2 6 9 34 19 19 18 18 17 17 16 16 15 15 15 14 13 13 .6 .0 .5 .0 .5 .0 .6 .2 .8 .4 .0 .3 .6 .3 7 8 3 3 6 8 7 5 3 4 8 6 7 1 35 20 19 19 18 18 17 17 16 16 16 15 14 14 13 .3 .7 .2 .6 .2 .7 .3 .8 .4 .0 .6 .9 .2 .9 6 8 2 9 2 5 1 9 7 8 9 7 8 2 36 21 20 19 19 18 18 17 17 17 16 16 15 14 14 .0 .4 .8 .3 .8 .4 .9 .5 .1 .7 .3 .6 .8 .5 6 7 9 6 9 2 7 3 1 2 3 1 9 3 37 21 21 20 20 19 19 18 18 17 17 16 16 15 15 .7 .1 .5 .0 .5 .0 .6 .1 .7 .3 .9 .2 .5 .1 5 4 8 6 6 8 1 9 8 6 7 2 0 4 38 22 21 21 20 20 19 19 18 18 18 17 16 16 15 .4 .8 .2 .7 .2 .7 .2 .8 .4 .0 .6 .8 .1 .7 4 3 5 2 2 2 8 3 2 0 1 6 4 8 39 23 22 21 21 20 20 19 19 19 18 18 17 16 16 .1 .5 .9 .3 .8 .3 .9 .5 .0 .6 .2 .5 .7 .3 7 3 4 9 9 9 4 0 6 4 5 0 5 9 40 23 23 22 22 21 21 20 20 19 19 18 18 17 17 .8 .2 .6 .0 .5 .0 .5 .1 .7 .3 .8 .1 .3 .0 6 2 4 8 6 6 8 4 2 1 9 1 9 0 41 24 23 23 22 22 21 21 20 20 19 19 18 18 17 .5 .9 .3 .7 .2 .7 .2 .8 .3 .9 .5 .7 .0 .6 6 2 3 5 2 5 5 1 6 4 3 5 0 4 42 25 24 24 23 22 22 21 21 21 20 20 19 18 18 .2 .6 .0 .4 .9 .4 .9 .4 .0 .5 .1 .3 .6 .2 8 1 0 4 2 2 2 7 3 8 9 9 4 9 43 25 25 24 24 23 23 22 22 21 21 20 20 19 18 .9 .3 .6 .1 .5 .0 .5 .1 .6 .2 .8 .0 .2 .8 7 1 9 4 8 8 8 4 7 5 3 3 8 9 44 26 26 25 24 24 23 23 22 22 21 21 20 19 19 .6 .0 .3 .8 .2 .7 .2 .7 .3 .9 .4 .6 .8 .5 7 3 9 1 8 5 5 8 3 2 7 7 9 3 45 27 26 26 25 24 24 23 23 23 22 22 21 20 20 .3 .7 .0 .5 .9 .4 .9 .4 .0 .5 .1 .3 .5 .1 9 2 8 0 4 4 4 4 0 6 4 3 3 7 46 28 27 26 26 25 25 24 24 23 23 22 21 21 20 .0 .4 .7 .1 .6 .1 .6 .1 .6 .2 .7 .9 .1 .8 8 2 8 9 4 1 1 4 7 2 8 7 7 1 47 28 28 27 26 26 25 25 24 24 23 23 22 21 21 .8 .1 .4 .8 .3 .8 .2 .8 .3 .8 .4 .6 .8 .4 1 4 7 9 3 1 8 1 3 9 4 1 1 4 48 29 28 28 27 27 26 25 25 25 24 24 23 22 22 .5 .8 .1 .5 .0 .4 .9 .4 .0 .5 .1 .2 .4 .0 3 3 9 8 0 7 7 7 0 6 1 8 7 8 49 30 29 28 28 27 27 26 26 25 25 24 23 23 22 .2 .5 .8 .2 .6 .1 .6 .1 .6 .1 .7 .9 .1 .7 2 3 9 8 9 7 4 4 7 9 5 2 1 2 50 30 30 29 28 28 27 27 26 26 25 25 24 23 23 .9 .2 .5 .9 .3 .8 .3 .8 .3 .8 .4 .5 .7 .3 4 5 8 7 9 3 1 1 3 6 2 8 5 6 3.2 Computer implementation When computer facilities are available, it is possible to automate the use of Tables 3/E.521 to 6/E.521. For that purpose, numerical algorithms have been developed and are described in [5]. 4 Example 4.1 Level of day_to_day traffic variations If the traffics offered to a final group over the 30 busiest days are given (M1 to M30) and if the mean load and variance are calculated to be 10 and 20 respectively, then applying Figure 1/E.521, a high level of day_to_day traffic variations should be used. 4.2 Future traffic offered to the final group and peakedness factor If the forecast of future traffics indicates that three parcels of traffic will be offered to the final group: _ the overflow from 6 circuits offered 7.8 Erlangs, _ the overflow from 12 circuits offered 10 Erlangs, _ 7 Erlangs offered directly, then Table 7/E.521 can be developed. Table 7/E.521 Numbe Traff Numbe Adjus- Averag r of ic r of Single- Last Peake bizi temen e parce offer high- hour trunk dness t overfl ls of ed to usage overflow traff facto facto ow traff high- circu bi ic r zi r ri ic i usage it ni group Ai 1 7.8 6 2.95 0.69 1.73 5.1 1.0 2.95 2 10.0 12 1.20 0.44 2.19 2.6 1.2 1.44 3 7.0 0 7.0 _ 1.0 7.0 1.0 7.00 Note that the values of ri are derived from Table 2/E.521 for medium level of day_to_day traffic variations; if the 30 busiest day traffics for each of the high_usage groups were available, a more appropriate level could be used for each group. Now all the information required is available: using the capacity Table 6/E.521 for high level of day_to_day traffic variations, the average traffic offered to the final group M = 11.39 and a peakedness factor z = 1.3 (from interpolating between z = 1.2 and z = 1.4), it is calculated that 23 circuits are required. Note that if the measurements used in 4.1 above were not available, then to determine the level of day_to_day traffic variations it would have been necessary to use the default procedure of 1 above. Overflow traffic offered to the final group = 4.15 Erlangs. Total traffic offered to the final group = 11.15 Erlangs. The ratio 4.15/11.15 = 0.37 is higher than 0.25 and hence a medium level of day_to_day traffic variations would have been used. References [1] Tabellen fr die Planung von Fernsprecheinrichtungen, Siemens u. Halske, Mnchen, 1961. [2] WILKINSON (R. I.): Theories for toll traffic engineering in the USA (Figures 12 and 13), Bell System Technical Journal, Vol. 35, March 1956. [3] WILKINSON (R. I.): Simplified engineering of single stage alternate routing systems, Fourth International Teletraffic Congress, London, 1964. [4] WILKINSON (R. I.): Non_random traffic curves and tables, Bell Telephone Laboratories, 1970. [5] HILL (D. W.) and NEAL (S. R.): The traffic capacity of a probability_engineered trunk group, Bell System Technical Journal, September 1976. _______________________________ 1) Tables giving: _ the exact mean of the overflow traffic, and _ the difference between variance and mean of the overflow have been computed and are set out in [1]. 2) Curves giving the exact mean and variance of overflow traffic are given in [2]. See also a more detailed description of the method in [3] and [4].